The Manischewitz Company, whose matzo and gefilte fish are a staple of Seder tables around the world, is expected to announce on Tuesday that it has been sold to Sankaty Advisors, an arm of the private equity giant Bain Capital. The deal, just in time for Passover next week, may help the 126-year-old company expand beyond the kosher aisle.

Manischewitz, a household name among Jews but with lower visibility outside its niche, is trying to capitalize on the mainstream craze for pure and healthy food. Under its new owner, a firm with expertise in revamping corporate strategy, the company is expected to promote “kosher” as a quality-control designation, rather than a simply a religious one.

“It’s a pretty powerful certification to be kosher, because it means you are holding your product to a very high standard,” Mark Weinsten, the newly appointed interim chief executive of Manischewitz, who is also a senior managing director at FTI Consulting, said in an interview. “Why is that not applicable to people who don’t keep kosher?”

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Matzos made at Manischewitz plant in Newark.Credit Sylwia Kapuscinski for The New York Times

The maker of macaroons and chicken broth has bounced around among various owners over the last two decades.

Founded in 1888 as a small matzo bakery in Cincinnati, Manischewitz grew into a kosher food empire, controlling 80 percent of the United States matzo market by 1990. That year, the company was sold to Kohlberg & Company, a private equity firm.

Eight years later, it changed hands again and took a new name: the R.A.B. Food Group. In 2008, after a new investment from Philip A. Falcone’s hedge fund, Harbinger Capital Partners, the company that was founded by Rabbi Dov Behr Manischewitz reclaimed the family name.

Sankaty, which had been a lender to Manischewitz, now owns all of the company’s equity. The deal’s price was undisclosed.

Though private equity tends to conjure images of stripping and flipping companies, Sankaty plans to act as “stewards of the brand,” said a person briefed on the deal who was not authorized to speak publicly about it before the announcement.

Mr. Weinsten, the new leader, is a serial C.E.O. who in the past has run a number of other small companies in need of fresh thinking. He grew up attending temple and eating Manischewitz products at Passover, but, in a sign of the company’s ambitions to appeal to the mainstream, says he considers himself a Reform Jew.

“There is, I believe, a consensus among American consumers that the more supervision the better,” Rabbi Yaakov Y. Horowitz, the company’s chief rabbi, said in an interview. “There was always a good feeling in American culture about kosher.”

The company estimates that roughly 60 percent of its products are now sold in kosher aisles of supermarkets. But by introducing new products and relying on more mainstream foods like sardines and soup, it hopes to shift that balance.

Manischewitz is also trying to stay abreast of the latest in food trends, including by offering gluten-free items. Mr. Weinsten said his daughters would be enjoying gluten-free Manischewitz fare at their family’s Seder next week.

The push to revamp the product lineup has been in the works for some time, though it experienced a hiccup several years ago. The company in 2008 temporarily stopped making its popular Tam Tam crackers after problems with new equipment at its Newark factory, creating a conspicuous absence on Seder tables.

But the issues were smoothed out the next year. The company relocated its headquarters to Newark from Secaucus in 2011 and celebrated the occasion by making a 25-foot-long matzo. Cory Booker, the Newark mayor at the time, was quoted as saying that the company’s arrival “gives me great naches,” a Yiddish word meaning proud delight.

Around that time, the company also introduced advertisements that took a secular approach, with scant mention of religious themes.

Rabbi Horowitz, though he was not involved in the private equity deal, said he had a “very positive feeling” about the new owners.

“To a good number of American Jews — perhaps a large number of American Jews, those that are unaffiliated and Reform — Manischewitz is the last link to their religion, almost,” the rabbi said. “The last thing that Jews let go, if they’re acculturating to the extreme,” will be the Passover Seder.

Correction: April 19, 2014An article on April 8 about the sale of the Manischewitz Company to an arm of the private equity giant Bain Capital described part of the company’s history incorrectly. At the time of its 1990 sale to Kohlberg & Company, Manischewitz was publicly listed, not family-owned. Also, the sale was negotiated through the board; the company was not “sold by a grandson of the founder.”

A version of this article appears in print on 04/08/2014, on page B4 of the NewYork edition with the headline: Equity Fund Buys Maker of Matzos.